1. Field of the Invention
The present invention relates to a packaging system configured to package a product by covering the top surface of the product with a film.
2. Background Information
In conventional practice, some packaging systems package products with films by means of raising a container, such as a tray or the like, having a product contained therein onto a packaging station arranged thereabove. One example of such a packaging system is shown in FIGS. 8 and 9.
When a product M is placed on a tray supply device 20 shown in FIG. 8 by an operator, the rear end Tb of the tray (container) T carrying the product M is pushed by a conveying bar (contact member) 13, and the tray T is conveyed onto a lifter 201. The posts 210 of the lifter 201 are disposed directly beneath the packaging station S of a packaging unit 200. The posts are capable of being raised and lowered by a hoisting device 208. The lifter 201 lifts the product M up to the packaging station S when the product M is supplied from the tray supply device 20 thereto.
Before the packaging operation, a film F cut to a specific length is supplied to and stretched over the packaging station S in FIG. 9A by a film supply device 202 (shown in FIG. 8). This film F adheres to the top surface of the product M when the product M is pressed upward. In this state, a film folding unit 203 packages the product M by folding the edges on all four sides of the film F onto the bottom side of the tray T with a pair of left and right folding plates 204, 204, a rear folding plate 205, a rod-shaped front folding member 206, and a pusher 207 (shown in FIG. 8), and the packaged product M is ejected onto an ejecting conveyor 209 shown in FIG. 8.
However, the tray T may be somewhat misaligned to the left or right because it is placed on the tray supply device 20 by an operator. In order to solve this problem in this type of conventional packaging system, as disclosed in Japan Patent Application Publication 2001-48109 (particularly FIG. 5 thereof), the amount by which the tray T is misaligned in the width direction on the tray supply device 20 is determined, and this widthwise misalignment is corrected in order to improve the finished state of packaging.
In a conventional packaging system, as shown in FIG. 6A, the tray T is photographed from above by a camera when the tray T is placed on the tray supply device 20 (shown in FIG. 8). The amount of misalignment from the center of the tray T is calculated based on this photograph information. After the photographing, the tray T is conveyed by a conveying bar 13, as shown in FIG. 6B, and then the tray T is moved towards the center by a movement unit (not shown in the figures) according to the amount of misalignment, as shown in FIG. 6C.
However, sometimes the amount of misalignment changes when the conveying bar contacts with the tray, due to factors such as the weight of the materials to be packaged, the center of gravity, and the friction between the underside of the tray and the scale tray, even if the tray is positioned in the same manner and at the same position. For example, when the tray T is placed so as to be tilted with respect to the conveying bar 13, as shown in FIGS. 6D and 6E, the amount of post-conveyance misalignment of the tray T after it is conveyed and in contact with the conveying bar 13 may differ from the calculated misalignment, as shown in FIGS. 6D and 6E. Therefore, sometimes the misalignment cannot be sufficiently corrected, even if the tray T is moved towards the center in accordance with the amount of misalignment determined by the camera.
Thus, sometimes the misalignment in the width direction, which is substantially orthogonal to the conveying direction of the products, cannot be resolved from the time conveying is initiated by the conveying unit until the time conveying is completed.
An inadequately corrected misalignment sometimes brings about a misalignment in the position of the product during packaging or a misalignment in the label attachment position. As a result, packaging is unsatisfactory, or the attachment position is misaligned. In addition, a large misalignment may even cause the tray T to be crushed.
Furthermore, misalignment can also occur in the conveying direction of the product.
FIGS. 7A-7H are schematic side views showing the vicinity of the tray supply device 20 and a lifter 201. FIGS. 7A and 7B show a normal conveying state of the tray T. The tray T shown in FIG. 7A is pushed by the conveying bar 13, and is conveyed onto the lifter 201 as shown in FIG. 7B. The position (stopping position) of the end of the advancing movement of the conveying bar 13 is set in advance for each tray T, and the tray T is pushed and conveyed to a specific position on the lifter 201 according to this set stopping position.
However, in cases such as when a tray T carrying a product is light in weight, as shown in FIGS. 7C and 7D, the conveying bar 13 sometimes slips underneath the tray T, and the tray T will not be conveyed to the specified position on the lifter 201 even if the conveying bar 13 stops at the set stopping position.
In addition, if the tray T is deep, as shown in FIGS. 7E and 7F, the conveying bar 13 sometimes slips in underneath the edge of the tray T, and the tray T will not be conveyed to the specified position on the lifter 201.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved packaging system. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.